Process of purifying tanning liquids.



Thurman STATES FFICE,

' ATENT ALBERT THOMPSON, OF PARIS, AND EMILE BLIN, )F NANTES, FRANCE.

PROCESS OF PURIF YING TANNING LIQUIDS.

SPECIFICATION forming part of Letters Patent No. 671,570, dated April 9, 1901.

Application filed February 19, 1900. Serial No. 5,834- (No specimens.)

1'0 ail w/wm it may concern:

Be it known that we, ALBERT THOMPSON, residing at Paris, and EMILE BLIN, residing at Nantes, France, citizens of France, have invented certain new and useful Improvements in Processes of Clarifying Tanning Liquids; and we do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

Our invention relates to a process of clarifying tanning liquids employed in the tanning of skins for the preparation of leather.

The mineral acids (take,for instance,sulfuric acid) precipitate salts of lime and destroy certain organic properties contained in the tanning liquor and bring about their discoloration; but these acids have a disastrous effect upon the tanning,because they favor oxidation, (especially under heat,) and it must not be forgotten that the products of oxidation of physiological tanning precipitate neither gelatin nor albumin. They are therefore useless; but, on the other hand, they give a black coloring with the salts of copper and iron and are consequently prejudicial. Heretofore the tanning liquid, generally obtained by a diffusion in boiling water of certain woods rich in tanning properties, was poured out of the diffusing-tub upon attaining 3 or 4 Baum. The liquid is then elarified,amoug the substances used being sulfuric or other acid, with the object of precipitating or destroying the salts and colored organic matters contained. The clarifying performed, the liquid is filtered to deprive it of deposits arising from the clarifying operation and is then concentrated in an evaporating apparatus up to a density of and Baum, or even more. The tanning liquids thus treated by acids are impoverished to a great extent in their useful qualities. Further, the oleaginous products employed generally in the acid processes to counteract the destructive effect of these acids and give to the tanning liquid the softness which said acids take from it present many disadvantages, notably that of forming stains or spots and to spoil the density of the tanning liquid proper. In

accordance with our invention the tanning liquids, always obtained by diffusion, are

clarified without employing either acids or oleaginous matters and contain proportionately more useful properties than the tanning liquors treated by the acid process. They contain no acids nor other matters likely to alter their actual density. A series ofmethodical experiments has led us to employ vegetable alkaloids, and we give the preference to the vegetable basis naturally contained in the sulfates of quinquina quinin, quinidine, cinehonine, cinchonidine, and their derivatives. We may use one of these alkaloidal salts separately or a mixture of any two or more of them and prefer them to the pure salts, as they are cheaper, more readily obtainable, and possess greater solubility. The pure alkaloids are susceptible of use with some difficulty on account of their slight solubility. All the alkaloidal salts are readily susceptible of use.

We manufacture the tanning liquor in the following manner: The liquid leaving the diffusingtub possesses a density varying from 3 to 4 Baum, (the degree being obtained at will.) It is left to cool to the surrounding temperature. The cooling effected,

we pour in a solution of salts of the alkaloids,

of quinquina (weakened by water or pure, to suit requirements) and then agitate strongly for about five minutes. The alkaloid salts are in proportions of one, two, or three kilograms to the thousand kilograms of tanning acid brought to 20 Baum, according to the discoloration required; but the proportions may be varied according to requirements.

Under the action of these alkaloids the colored or foreign organic matters, as well as a certain quantity of the tanning, are precipitated at the same time as the alkaloids, and this while leaving to the liquor the gloss or glaze so generally appreciated. We should state that the operations may be carried on at any temperature; but we prefer the cold treatment to the hot, as the performance is much quicker. The deposit of clarification in which is found the major part of the vegetable alkaloids is drained and is treated at a warmtemperature with water acidnlated with .005 of hydrochloric acid. The liquid is filtered and treated with a solution of ten grams of quicklime to a liter of hydrochloric acid. The alkaloids are precipitated with the excess of lime. The deposit is collected and washed in cold water and then treated by a slight excess of water acidulated by sulfuric acid. The liquid acid containing the alkaloids is filtered, discolored while warm by animal black, again filtered, and neutralized by the quinin or one of the other alkaloids precipitated by carbonate of soda in a part of the liquid.

Other processes of extraction may-be employed; but we mention the above to demonstrate the economy of our invention from an industrial point of view.

is claimed, and desired to be secured by Letters Patent, is

1. That step in the art or process of treati-ng tanning liquids for the purpose set forth, which consists in adding thereto an alkaloid of cinchona, substantially 'as set forth 2. That step in the art or process of treating tanning liquids for the purpose set forth, which consists in adding thereto an alkaloidal salt of cinchona, substantially as set forth.

3. That step in the art or process of treating tanning liquids, which consists .in adding thereto the sulfate ofan alkaloid of cinchona, substantially as set forth.

4. The herein-described process of clarifying tanning liquids, which consists in adding to the liquid an aqueous solution of a salt of an alkaloid of cinchona, substantially as set forth.

5. The herein-described process of clarifying tanning liquids, which consists in precipitating the foreign matter by the action of an alkaloid of cinchona, and then subjecting the deposit of clarification to the action of a substance capable of precipitating said alkaloid, substantially as set forth.

6. The herein-described process of clarifying tanning liquids, consisting in adding to the liquid an alkaloid of cinchona to precipitate the foreign matter, removing the deposits of clarification, subjecting the same to the action of acidulated water, precipitating the clarifying agent by the action of a lime-milk, and then neutralizing the said clarifying agent, substantially as set forth. Having thus described the invention, what 7. That step in the art or process of treating the residue of clarified tanning liquids which consists in collecting the deposits of clarification, subjecting the same to the action of Water acidulated by the addition of .005 per cent. of hydrochloric acid thereto, precipitating the clarifying agentby the action of a lime-milk in proportion often grams of quick-lime to a liter of the hydrochloric acid employed in the preceding step, and then neutralizing the said clarifying agent, substantially as described.

In testimony whereof We have hereunto set our hands in presence of subscribing witnesses. v

ALBERT THOMPSON. EMILE BLIN. Witnesses as to Albert Thompson:

EDWARD P. MACLEAN, ANTOINE ANGIER. Witnesses as to Emile Blin:

EDMOND THADDORE, GIRET HENRI. 

